全文获取类型
收费全文 | 7002篇 |
免费 | 115篇 |
国内免费 | 14篇 |
专业分类
电工技术 | 361篇 |
综合类 | 6篇 |
化学工业 | 1331篇 |
金属工艺 | 197篇 |
机械仪表 | 155篇 |
建筑科学 | 104篇 |
矿业工程 | 1篇 |
能源动力 | 206篇 |
轻工业 | 485篇 |
水利工程 | 31篇 |
石油天然气 | 7篇 |
无线电 | 643篇 |
一般工业技术 | 1207篇 |
冶金工业 | 1830篇 |
原子能技术 | 146篇 |
自动化技术 | 421篇 |
出版年
2023年 | 24篇 |
2022年 | 59篇 |
2021年 | 114篇 |
2020年 | 47篇 |
2019年 | 52篇 |
2018年 | 76篇 |
2017年 | 73篇 |
2016年 | 76篇 |
2015年 | 85篇 |
2014年 | 93篇 |
2013年 | 235篇 |
2012年 | 202篇 |
2011年 | 275篇 |
2010年 | 187篇 |
2009年 | 227篇 |
2008年 | 226篇 |
2007年 | 254篇 |
2006年 | 237篇 |
2005年 | 206篇 |
2004年 | 191篇 |
2003年 | 180篇 |
2002年 | 184篇 |
2001年 | 171篇 |
2000年 | 151篇 |
1999年 | 179篇 |
1998年 | 670篇 |
1997年 | 426篇 |
1996年 | 321篇 |
1995年 | 218篇 |
1994年 | 224篇 |
1993年 | 182篇 |
1992年 | 105篇 |
1991年 | 101篇 |
1990年 | 97篇 |
1989年 | 90篇 |
1988年 | 80篇 |
1987年 | 65篇 |
1986年 | 74篇 |
1985年 | 89篇 |
1984年 | 59篇 |
1983年 | 64篇 |
1982年 | 51篇 |
1981年 | 56篇 |
1980年 | 58篇 |
1979年 | 37篇 |
1978年 | 31篇 |
1977年 | 58篇 |
1976年 | 65篇 |
1975年 | 35篇 |
1973年 | 29篇 |
排序方式: 共有7131条查询结果,搜索用时 0 毫秒
31.
H Yasoshima K Uematsu K Sakurai Y Ueno K Hori N Kanazawa T Tanaka N Yamanaka E Okamoto 《Canadian Metallurgical Quarterly》1993,43(12):783-789
A case of primary carcinoid tumor arising in the liver of a 69 year old woman with no endocrine symptoms is reported. Histopathologically, the tumor was diagnosed initially as a hepatocellular carcinoma in the biopsy specimen, and was shown subsequently to be a carcinoid tumor, demonstrating diffuse positive staining with Grimelius method. Mucin stained with periodic acid-Schiff (PAS), alcian-blue, and mucicarmine, and was shown partially in the glandular structures. Immunohistochemically, most of the tumor cells stained positively for chromogranin-A, epithelial membrane antigen (EMA) and neuron specific enolase (NSE). Ultrastructural examination revealed electron-dense core granules, measuring 40-120 nm in diameter in some of the tumor cells. Intensive and careful searches pre- and post-operatively revealed no other primary source of tumor other than the liver. The patient was reported well with no symptoms 3 1/2 years after the operation. This case is considered to be a primary hepatic carcinoid tumor. The recent literature is reviewed, and the possible histogenesis of hepatic carcinoid tumor is discussed. 相似文献
32.
An AlGaAs/GaAs micromachining technique that is compatible with laser diode fabrication process is described. AlGaAs structural layers and GaAs sacrificial layers are prepared by metal organic vapor phase epitaxy. Reactive dry etching with chlorine is used to fabricate high-aspect structures. Peroxide/ammonium hydroxide solution is used for selective etching of the sacrificial layer. Since the epitaxial layer has low stress, precise undeformed microstructures are obtained. Good compatibility with the LD process makes it possible to integrate microcantilever beams with LD's without degradation of LD characteristics. Microcantilever beams of AlGaAs are characterized by directly measuring stiffness and natural frequencies. A fracture test is also performed on the AlGaAs microcantilever beams. The average fracture stress of AlGaAs is found to be 1 GPa at 1% strain, which shows that the material is strong enough to support the micrometer scale structures 相似文献
33.
34.
Thiamine pyrophosphatase activity in the Golgi apparatus of calcitonin-treated osteoclasts. 总被引:1,自引:0,他引:1
The thiamine pyrophosphatase (TPPase) activity described by Novikoff and Goldfisher was examined in osteoclasts affected by calcitonin in order to elucidate whether the morphological and functional changes of the osteoclasts have an influence over the secretion function of their Golgi apparatus. The Golgi apparatus of osteoclasts of which the ruffled border had disappeared and bone resorption discontinued as the result of treatment with calcitonin showed a slight TPPase activity. The reaction products of the enzyme in these inactive osteoclasts were distinctly fewer than that of control osteoclasts, which were not affected by calcitonin. From these results, it is suggested that there may be a connection between the morphological and functional changes of osteoclasts and the secretion function of the Golgi apparatus. 相似文献
35.
We have developed a Zimm-type viscometer specially designed for the simultaneous measurements of the structure factor and the viscosity of hyperswollen lyotropic liquid crystals under a very weak shear. We have investigated the shear effects on the layer undulation fluctuation in the lamellar structure and the transition from the anisotropic lamellar to the isotropic sponge phase. We have found a significant difference in the rheological properties between the lamellar and the sponge phase: The former exhibits non-Newtonian flow behavior, while the latter exhibits Newtonian behavior.Paper presented at the Twelfth Symposium on Thermophysical Properties, June 19–24, 1994, Boulder, Colorado, U.S.A. 相似文献
36.
This paper deals with a new boundary element method for analysis of the quasistatic problems in coupled thermoelasticity. Through some mathematical manipulation of the Navier equation in elasticity, the heat conduction equation is transformed into a simpler form, similar to the uncoupled-type equation with the modified thermal conductivity which shows the coupling effects. This procedure enables us to treat the coupled thermoelastic problems as an uncoupled one, A few examples are computed by the proposed BEM, and the results obtained are compared with the analytical ones available in the literature, whereby the accuracy and versatility of the proposed method are demonstrated. 相似文献
37.
We developed a multichannel fiber ferrule for a stable laser-diode array module. To apply YAG laser welding to parallel butt couple between the laser-diode and the single-mode fiber arrays, hermetically sealed and precisely aligned equi-interval fibers are required. We describe a V-grooved ceramic ferrule for embedding fibers. Fibers are fixed by soldering, using a flat ceramic lid and aligned with a 250 μm pitch. Our ferrule allowed a metallic, stem mounting laser-diode, to be fixed by YAG laser welding. All 30 samples tested have a leak rate of less than 1×10-10 atm·cc/s. Optical coupling of fabricated modules was 9.7±0.2 dB and coupling loss change from 25°C to 115°C was within 0.5 dB 相似文献
38.
Bargiela A. Pedrycz W. Tanaka M. 《IEEE transactions on systems, man, and cybernetics. Part A, Systems and humans : a publication of the IEEE Systems, Man, and Cybernetics Society》2003,33(3):288-301
In this paper, we present results of uncertain state estimation of systems that are monitored with limited accuracy. For these systems, the representation of state uncertainty as confidence intervals offers significant advantages over the more traditional approaches with probabilistic representation of noise. While the filtered-white-Gaussian noise model can be defined on grounds of mathematical convenience, its use is necessarily coupled with a hope that an estimator with good properties in idealised noise will still perform well in real noise. In this study we propose a more realistic approach of matching the noise representation to the extent of prior knowledge. Both interval and ellipsoidal representation of noise illustrate the principle of keeping the noise model simple while allowing for iterative refinement of the noise as we proceed. We evaluate one nonlinear and three linear state estimation technique both in terms of computational efficiency and the cardinality of the state uncertainty sets. The techniques are illustrated on a synthetic and a real-life system. 相似文献
39.
Tooru Tanaka Toshiyuki Yamaguchi Akihiro Wakahara Akira Yoshida Ryoichi Taniguchi Yatsuka Matsuda Masatoshi Fujishiro 《Solar Energy Materials & Solar Cells》2003,75(1-2):115-120
Radiation damages due to 8 MeV electron irradiation in electrical properties of CuInSe2 thin films have been investigated. The n-type CuInSe2 films in which the carrier concentration was about 3×1016 cm−3, were epitaxially grown on a GaAs(0 0 1) substrate by RF diode sputtering. No significant change in the electrical properties was observed under the electron fluence <3×1016 e cm−2. As the electron fluence exceeded 1017 e cm−2, both the carrier concentration and Hall mobility slightly decreased. The carrier removal rate was estimated to be about 0.8 cm−1, which is slightly lower than that of III–V compound materials. 相似文献
40.
Remi Kasai Hideaki Yaegashi Hiroshi Yokoyama Masahiko Yamanaka Hideo Sawada 《Journal of Materials Science》2007,42(24):10228-10238
Fluoroalkanoyl peroxides reacted with FULLERENES [fullerene (C60) and commercially available fullerenes (Nanom MixTR and Nanom BlackTR)] and radical polymerizable comonomers such as acrylic acid, N,N-dimethylacrylamide, N-(1,1-dimethyl-3-oxobutyl)acrylamide, and acryloylmorpholine to afford fluoroalkyl end-capped cooligomers having FULLERENES
in the main chain under very mild conditions. Fluoroalkyl end-capped Nanom Mix and Nanom Black cooligomers thus obtained were
found to exhibit a similar solubility to that of the corresponding fluoroalkyl end-capped cooligomers having fullerene in
the main chain. These fluorinated FULLERENES cooligomers were found to form the nanometer size-controlled self-assembled cooligomeric
aggregates in aqueous solutions. These fluoroalkyl end-capped FULLERENES cooligomers were more effective for solubilizing
fullerene, Nanom Mix and Nanom Black into water, compared to those of the corresponding fluoroalkyl end-capped homooligomers
having no FULLERENES in the main chain. Fluoroalkyl end-capped fullerene- and Nanom Mix-acrylic acid cooligomers were found
to exhibit fluorescence spectra related to fullerene and Nanom Mix in cooligomers, respectively, in aqueous solutions. Additionally,
these fluorinated fullerene- and Nanom Mix-acrylic acid cooligomers were able to increase chemiluminescence intensity related
to luminol, effectively, compared to the corresponding fluorinated acrylic
acid homooligomers. 相似文献